Kidney Pt. 2

Question 1

When does kidney dysfunction become apparent?

Answer 1

When the kidney is at <25% of normal functionality.

Question 2

What happens when one kidney starts to fail?

Answer 2

1. The remaining nephrons in that kidney adapt to handle the larger than normal load.
2. The other kidney will take on more of the filtration load.

Question 3

What happens when one kidney is surgically removed?

Answer 3

The remaining kidney hypertrophies to filter blood at 80% of the rate of 2 kidneys.

Question 4

What are the 3 basic functions of the nephron?

Answer 4

1. Glomerular filtration.
2. Tubular reabsorption.
3. Tubular secretion.

Question 5

What occurs during glomerular filtration?

Answer 5

Water and most solutes in the blood plasma move across the wall of the glomerular capillaries into the glomerular capsule and into the renal tubule.

Question 6

What occurs during tubular reabsorption?

Answer 6

The filtered fluid flows along the renal tubule and through collecting ducts as ~99% of filtered water and useful solutes are reabsorbed by tubule cells.

Question 7

How does reabsorbed water and solutes return to the main blood supply?

Answer 7

Peritubular capillaries and vasa recta.

Question 8

What occurs during tubular secretion?

Answer 8

Fluid flows through renal tubules and through collecting ducts, the tubule and duct cells secrete waste, drugs, and excess ions into the filtered fluid.

Question 9

What is the fluid that enters the capsular space called?

Answer 9

Glomerular filtrate.

Question 10

What is the daily volume of glomerular filtrate in adult females?

Answer 10

150 L.

Question 11

What is the daily volume of glomerular filtrate in adult males?

Answer 11

180 L.

Question 12

How many liters of urine are excreted by the average adult daily?

Answer 12

1-2 liters.

Question 13

What are the 3 barriers that substances filtered in the glomerulus must cross?

Answer 13

1. Glomerular endothelial cells.
2. Basal lamina.
3. Filtration slits formed by podocytes.

Question 14

What is the filtration membrane described as?

Answer 14

A leaky barrier.

Question 15

What is the filtration membrane composed of?

Answer 15

1. Endothelial cells of glomerular capillaries.
2. Podocytes.

Question 16

What does glomerular filtration permit filtration of?

Answer 16

1. Small solutes.
2. Water.

Question 17

What does glomerular filtration prevent filtration of?

Answer 17

1. Blood cells.
2. Plasma proteins.
3. Platelets.

Question 18

What do glomerular endothelial cells contain?

Answer 18

Fenestrations/large pores.

Question 19

What do these fenestrations permit?

Answer 19

All solutes in the blood plasma to exit glomerular capillaries with the exception of blood cells and platelets.

Question 20

What are mesangial cells and what is their function?

Answer 20

Contractile cells that help regulate filtration.

Question 21

Where are mesangial cells located?

Answer 21

1. Among the glomerular capillaries.
2. In the cleft between afferent and efferent arterioles.

Question 22

What is the basal lamina and what is its function?

Answer 22

The layer of material between endothelium and podocytes in the glomerulus that prevents filtration of larger plasma proteins.

Question 23

What is the basal lamina composed of?

Answer 23

1. Minute collagen fibers.
2. Proteoglycan.

Question 24

What are filtration slits and what is their function?

Answer 24

The spaces between pedicels covered by slit membranes that permit the passage of smaller diameter molecules.

Question 25

What molecules pass through the filtration slits and slit membranes?

Answer 25

1. AA's. 2. Ammonia. 3. Ions. 4. Glucose. 5. Urea. 6. Very small plasma proteins. 7. Vitamins. 8. Water.

Question 26

What are the 3 main pressures that contribute to net filtration pressure?

Answer 26

1. Glomerular blood hydrostatic pressure (GBHP). 2. Capsular hydrostatic pressure (CHP). 3. Blood colloid osmotic pressure (BCOP).

Question 27

Which type(s) of pressure promotes filtration?

Answer 27

GBHP.

Question 28

Which type(s) of pressure oppose filtration?

Answer 28

1. CHP. 2. BCOP.

Question 29

What is GBHP?

Answer 29

The blood pressure in glomerular capillaries that promotes filtration by forcing water and solutes in blood plasma through the filtration membrane.

Question 30

What is the GBHP in mmHg?

Answer 30

~55.

Question 31

What is CHP?

Answer 31

The hydrostatic pressure exerted against the filtration membrane by fluids already in the capsular spaces and renal tubules. A form of "back pressure".

Question 32

What is the CHP in mmHg?

Answer 32

~15.

Question 33

What is BCOP?

Answer 33

The pressure exerted as a result of proteins in the blood plasma attracting fluid back into the blood.

Question 34

What is BCOP in mmHg?

Answer 34

~30.

Question 35

How is net filtration pressure (NFP) calculated?

Answer 35

NFP= GBHP-CHP-BCOP.

Question 36

What is the NFP of a normal kidney?

Answer 36

10 mmHg promoting filtration.

Question 37

What is the amount of filtrate formed in all renal corpuscles in both kidneys each minute in females?

Answer 37

125 mL.

Question 38

What is the amount of filtrate formed in all renal corpuscles in both kidneys each minute in males?

Answer 38

105 mL.

Question 39

Is GFR relatively constant?

Answer 39

Yes.

Question 40

What occurs is GFR is too high?

Answer 40

Substances pass too quickly through the renal tubules and may not be reabsorbed properly.

Question 41

What occurs if GFR is too low?

Answer 41

Nearly all the filtrate is reabsorbed and the waste products may not be properly excreted.

Question 42

What is GFR related to?

Answer 42

The pressures that determine net filtration pressure. ex: Severe blood loss leading to decreased arterial blood pressure leads the GBHP to be less than or equal to 45 mmHg, stopping filtration entirely.

Question 43

What are the 2 main ways that the GFR is regulated?

Answer 43

1. Adjusting blood flow into/out of the glomerulus. 2. Altering glomerular capillary surface area available for filtration.

Question 44

What are the 3 mechanisms that control GFR?

Answer 44

1. Renal autoregulation. 2. Neural regulation. 3. Hormonal regulation.

Question 45

What occurs during renal autoregulation?

Answer 45

The kidneys help maintain a constant renal blood flow through the myogenic mechanism and tubuloglomerular feedback.

Question 46

What is the myogenic mechanism?

Answer 46

The mechanisms that causes the contraction and relaxation of smooth muscle cells in the walls of the afferent arterioles in response to stretching.

Question 47

When blood pressure rises in response to the myogenic mechanism, what increases?

Answer 47

GFR in response to increased renal blood flow.

Question 48

What does increased renal blood flow and blood pressure cause to occur?

Answer 48

Stretching of the walls of the afferent arterioles, triggering a contraction of the smooth muscle cells in the walls of those blood vessels.

Question 49

What does the contraction of smooth muscles in the afferent arterioles cause?

Answer 49

Decreased renal blood flow and GFR.

Question 50

How long does it take for the myogenic mechanisms to normalize renal blood flow and GFR?

Answer 50

Seconds.

Question 51

What is tubuloglomerular feedback?

Answer 51

The macula densa providing feedback to the glomerulus due to elevated systemic blood pressure.

Question 52

What does tubuloglomerular feedback cause to occur in the renal tubules?

Answer 52

Filtered fluid to flow more rapidly.

Question 53

What is given less time to be absorbed in the PCT and LOH due to tubuloglomerular feedback?

Answer 53

1. Cl-. 2. Na+. 3. Water.

Question 54

What is inhibited in JGA cells when macula densa cells detect increased delivery?

Answer 54

The release of NO.

Question 55

What does NO cause?

Answer 55

Vasodilation.

Question 56

How fast is the feedback loop for tubuloglomerular feedback?

Answer 56

Slower than the myogenic mechanism.

Question 57

What are the renal blood vessels innervated by?

Answer 57

Sympathetic ANS nerve fibers.

Question 58

What neurotransmitter do the nerve fibers innervating the renal blood vessels release?

Answer 58

Norepinephrine.

Question 59

What does norepinephrine cause in renal blood vessels?

Answer 59

Vasoconstriction through targeting a1 receptors. *Plentiful in smooth muscles of afferent arterioles.

Question 60

What does the neural regulation of the renal blood flow look like at rest?

Answer 60

1. Sympathetic stimulation is low, so the arterioles are dilated. 2. Autoregulation of GFR prevails.

Question 61

How do afferent and efferent arterioles constrict under moderate sympathetic stimulation?

Answer 61

The same extent, restricting blood flow to the same extent in each.

Question 62

How do afferent and efferent arterioles constrict under greater sympathetic stimulation?

Answer 62

Vasoconstriction of the afferent arterioles are predominant.

Question 63

What happens with lower renal blood flow?

Answer 63

Reduced urine output to conserve blood volume and allow it to flow to other body tissues.

Question 64

What affect does angiotensin II have on the kidneys?

Answer 64

Reduces GFR.

Question 65

What affect does angiotensin II have on blood vessels?

Answer 65

Very potent vasoconstrictor.

Question 66

What affect does atrial natriuretic peptide (ANP) have on the kidneys?

Answer 66

Increase GFR.

Question 67

What is ANP secreted by?

Answer 67

Cells in the atria of the heart.

Question 68

What affect does ANP have on the kidney?

Answer 68

It causes relaxation of the glomerular mesangial cells, increasing capillary surface area available for filtration, increasing GFR rate.

Question 69

How often does filter fluid enter the PCT?

Answer 69

Every 30 minutes.

Question 70

Is the volume of filter fluid less than or greater than the amount of total blood plasma volume?

Answer 70

Greater than.

Question 71

What portion of the renal tubule makes the largest contribution to reabsorption?

Answer 71

The PCT.

Question 72

What solutes are absorbed during reabsorption?

Answer 72

1. Amino acids. 2. Ca2+. 3. Cl-. 4. Glucose. 5. HCO3-. 6. HPO4-. 7. K+. 8. Na+. 9. Urea.